Sub-Tenon's infiltration using bupivacaine 0.5% decreases acute postoperative pain.

EditorÐWe would like to thank Calenda and colleagues for contributing the results of their trial to the ongoing controversy over the use of sub-Tenon's block (STB) in posterior segment eye surgery. The use of STB continues to expand into all areas of ophthalmic surgery. A good evidence base for the choice of anaesthetic technique even in cataract surgery is unfortunately missing. The lack of good quality trials has recently been highlighted by others. 3 Given that Calenda's study was published as a letter, we accept that we are not given any details about power estimation, patient data, setting of the study, randomization methods, masking, or a description of the block procedure. But, we believe that the authors missed a valuable opportunity to reduce bias by not having a placebo control injection group. In studies assessing pain, this has proved essential. Calenda's results are solely based on comparing the mean pain scores. We would have liked information about the range as well, as this often reveals a more complete picture. Our most important criticism of the study is the failure to differentiate between the different types of posterior segment surgery. For example, scleral buckling surgery is far more painful postoperatively than a simple vitrectomy. Without these details, their case for using STB in all posterior segment operations is not convincing.